Which of the following is not true about Monteggia fracture dislocation -

Ans. is 'c' i.e., Ulna angulates posteriorly in the extention type Monteggia fracture dislocation:* This is a fracture of the upper-third of the ulna with dislocation of the head of the radius. It is caused by a fall on an out-stretched hand. It may also result from a direct blow on the back of the upper forearm.* These fall into two main categories depending upon the angulation of the ulna fracture - extension and flexion type. The extension type, is the commoner of the two, where the ulna fracture angulates anteriorly (extends) and the radial head dislocates anteriorly. The flexion type is where the ulna fracture angulates posteriorly (flexes) and the radial head dislocates posteriorly.* In a case with an isolated fracture of the ulna in its upper half, a dislocation of the head of the radius should be carefully looked for.* This is a very unstable injury, frequently redisplacing even if it has been reduced once. One attempt at reduction under general anaesthesia is justified. If reduction is successful, a close watch is kept by weekly check X-rays for the initial 3-4 weeks. In case, the reduction is not possible or if redisplacement occurs, an open reduction and internal fixation using a plate is performed. The radial head automatically falls into position, once the ulna fracture is reduced.* Malunion occurs commonly in cases treated conservatively, because of an undetected redisplacement within the plaster. It causes deformity of the forearm and limitation of elbow and forearm movements.